Various surgical devices are known for compressing and cutting different types of tissue. In general, these devices have an end effector, such as a pair of opposed jaw members, configured to engage tissue and a cutting mechanism that is configured to sever tissue engaged by the end effector. Certain of these devices can also be configured to apply energy, such as radio frequency (RF) electrical energy, to the tissue disposed between the jaws. The application of electrical energy in the vicinity of a tissue cut can seal the cut to prevent bleeding of the tissue and leakage of other fluids through the cut.
A common concern when using any of these devices is achieving hemostasis so that bleeding of the target tissue is limited. Energy density and tissue compression are factors in achieving hemostasis. High energy density can heat tissue too quickly resulting in excessive steam generation and/or charring of the tissue, while low energy density increases cycle time or may fail to heat the tissue to an adequate temperature to achieve a seal. By increasing the amount of pressure applied to the target tissue, the flow of blood can be limited, thereby decreasing the time necessary to achieve hemostasis. However, applying too much pressure can result in an unnecessary reduction in blood flow to the tissue surrounding the cut-line, potentially resulting in an elevated level of necrosis, a slower rate of healing, and/or a greater recovery period. Excessive compression can also mechanically separate or damage tissue preventing a seal. Inadequate compression will not approximate the two opposing sides of a vessel to achieve the seal. In a RF device in which jaw movement is about a pivot, the compressive force proximal to the pivot is greater than at a distal location which results in variation in energy density and tissue compression and thus inconsistent tissue sealing.
Accordingly, there remains a need for surgical devices and methods for energy density control during a tissue sealing process to improve seal consistency.